I like how this chapter is structured (and I like the brevity of your chapters in general, makes them very pleasant to read!)
Notice how, when Jez is being talked at by Mrs Flinns, the text is quite narrow? It kinda imitates the feeling of being followed and tagged on, and the repetition of 'Still nodding...' goes a ways to produce this feeling as well, it's like the text itself is being squeezed and pushed through the air with her rambling carrying behind.
I particularly liked, 'I think that her voice sounds like a hen clucking.' A really fun simile xD
A couple of things you might want to change;
- 'I suppose that this is supposed to be my breakfast. ' I don't think you need to repeat 'supposed', maybe just 'I suppose this is my breakfast.' is fine?
- ' As soon as I got down the stairs' and 'the bus came and I got to leave' Maybe just personal preference, but 'I got' is a really ugly word to use as a verb I think - it doesn't serve much purpose and reads a bit too colloquially, maybe 'I walked down the stairs' and 'the bus came and I made my escape.' would be a better alternative?
Keep up the good writing :)

This chapter adds an interesting dynamic to Jez's character, the hidden desire she has for drugs, is it something she's developed herself over time, or is it a longing to be like her mother? I like how your description of the burning smell outside, and the ' city air smells like. This is another kind of pollution. Another evil kind.' is quite ambiguous, and you describe this movement of people but the reader is left to their own imagination as to what exactly is happening - I like this subtlety with the description!
A line that is a bit hard to understand is, 'Rats, that's all they are. That are those nosy neighbours who can't mind their own business.' Are these 'Rats' the Flinns? And if they are, the second sentence reads a bit strangely - 'that are those' is a bit clumsy, maybe 'Rats, that's all they are. The nosy neighbours who can't mind their own business.' Reads a little bit cleaner, right?
Intrigued to see if Jez loses against those darker urges she has!

Really nice introductory chapter, you do what's probably most important in character drama-based stories, and that's introduce a strong narrative voice for your main character. I also like how you've gone for the present tense (and first person) delivery, it's one of the hardest ones to do well, but there it is!
One sentence that does read a little strange to me, is 'I'm not really a child anyone.' I'm not sure if this supposed to read 'anymore' or if's a more objective statement about not being any sort of person, if it's the latter I think it would read better 'I'm not really a 'child' anyone.' I hope that makes sense haha
The unconventional introduction with Trey and Jez is a nice change, I hope that indicates something a bit different than your off the shelf romance ;D